1. Field of the Invention
The present invention pertains to dispensing apparatus for liquid and pulverulent materials, and more particularly to such apparatus which is suitable for automated operation.
2. Description of the Related Art
Automated dispensing apparatus for pulverulent materials, such as food flavorings, chemical additives, paints, paint colorants and inks, for example, are becoming increasingly popular. Automatic dispensing machines have been developed for dispensing a plurality of different materials into a common container. These systems typically employ separate independent sources of material to be dispensed, with individual discharge mechanisms associated with their respective materials.
Examples of such apparatus are disclosed in commonly assigned U.S. Pat. Nos. 4,967,938 and 5,078,302. Formulations are stored in a digital computer or similar control device. Valve operating and pump operating equipment is provided at a dispensing station, located at a point adjacent a turntable carrying containers which hold the different materials. The valve operating and pump operating equipment is coupled to the computer. An operator selects a particular formula (e.g., by name) from a list of formulas stored in the computer. When the formulation is identified, the computer indicates the first canister to be selected. For example, when the material being dispensed is a coloring, such as a tint for a paint base, the computer identifies which color tint is to be dispensed first.
The container may simply be identified on an output device, such as a cathode ray tube, with the system pausing until confirmation by the operator that the particular canister is in the desired position, or alternatively, the control system may index the turntable automatically, to bring the canister to the dispensing station. An example of a semi-automatic dispensing apparatus in which the turntable is manually indexed by an operator is described in commonly assigned U.S. Pat. No. 5,119,973. When the container is in place, the computer then directs the valve operator to open necessary valves for a dispensing operation and to prepare the pump operator for a pumping stroke. Under computer control, the pump associated with each container is operated so as to discharge an amount called for by the selected formula. After the pumping operation is completed, the computer calls for closing of the necessary valves, and the cycle is repeated for a second container (e.g., a second color tint to be added to the paint base). As with the fully automatic systems, the valve operation and pump operation of U.S. Pat. No. 5,119,973 is under computer control.
In each of the above-mentioned United States Letters Patent, a single dispensing pump is associated with each storage container. Commonly assigned U.S. Pat. No. 4,027,785 discloses a dual pump colorant dispenser offering improved metering accuracy, with a large pump dispensing large quantities of material, and a small pump dispensing small quantities of material so as to more accurately achieve a total dispensed amount. However, the dual pump dispenser has been developed for and has found ready commercial acceptance as a manually operated device.
Improvements are still being sought in automatic dispensing equipment, and it would be desirable to provide improved metering accuracy with a minimum of development time and cost of production.